1. Field of the Invention
The present invention relates to a resonator and a band pass filter using the same, and more particularly, to a laminated resonator and a laminated band pass filter using the same, used in a portable telephone set.
2. Description of the Related Art
A conventional resonator as shown in FIG. 16, includes a dielectric substrate 192 having a conductor 93 over the entire back thereof and a strip conductor 94 on the surface thereof. The resonator further comprises another dielectric substrate 192 having a conductor 93 over the entire surface thereof, bonded to the first-mentioned substrate 192 with the strip conductor 94 in between to achieve a laminated structure. Assuming that the length of this strip conductor 94 is L, the central wavelength of the resonator is .lambda., and the specific inductive capacitance of the dielectric substrate is .epsilon., then the following formula (1) applies: EQU L=(.lambda./4).times.(1/.epsilon.).sup.1/2 ( 1).
In the conventional resonator, however, it is difficult to downsize the resonator, because the strip conductor 94 is required to have a length L satisfying the relationship of the formula (1). Further, the strip conductor 94 and other resonator parts are typically configured to satisfy strict dimensional tolerances, thereby rendering the manufacture of the resonator difficult.
Another conventional band pass filter, as shown in FIG. 38, comprises a dielectric substrate 102 having conductor 103 over the entire back thereof, and two strip conductors 104 which are .lambda./4 resonators on the surface of the dielectric substrate. The two strip conductors 104 are configured to be separated by a distance (D) of about .lambda./4. The band pass filter further comprises another dielectric substrate 102 having a conductor 103 over the entire surface thereof, bonded to the first dielectric substrate 102 with the strip conductors 104 in between to achieve a laminated structure. Assuming that the length of the strip conductors 104 is L, the central wavelength is .lambda., and the specific inductive capacity of the dielectric substrate is .epsilon., then the foregoing formula (1) applies.
However, it is difficult to downsize conventional band pass filters, because the strip conductors are required to have a length L satisfying the relationship of the formula (1). Further, configuring the strip conductors 104 and other band pass filter parts in compliance with strict dimensional tolerances renders the manufacture of the band pass filter difficult.